DESCRIPTION: (Adapted from the Applicant's Abstract.) The goal of the proposed research is to improve our basic understanding of the peripheral auditory system through mathematical analysis and computer simulation of cochlear mechanics. In recent years, models of cochlear mechanics with active elements helped to motivate physiologic research on outer hair cell motility. The motility of outer hair cells and their influence on cochlear mechanics remains a topic of considerable interest among physiologists. The present proposal will continue research on active and nonlinear models of cochlear mechanics. The emphasis will be on (1) establishing a physical basis for active elements in the cochlea which are essential for achieving sharp tuning and high sensitivity, (2) deriving an explicit representation for functional nonlinearity in the cochlea which serves to compress the large dynamic range of inputs to the ear into a smaller dynamic range of inputs to the auditory nerve, (3) simulating the intensity dependent travel time of acoustic transients typical of the human cochlea and (4) providing a framework for understanding independent measures of cochlear function such as otoacoustic emission and the auditory brainstem response in normal, impaired, and developing cochleas. Specific objectives are (1) to learn more about the influence of outer hair cells on cochlear mechanics, (2) to account for the decrease observed in latency with increasing intensity both in auditory brainstem responses and in otoacoustic emissions over a wide range of tone burst frequencies, (3) to simulate the influence of external tones on spontaneous acoustic emissions, (4) to simulate normal and abnormal growth of loudness observed in ears with and without functioning outer hair cells, and (5) to derive algorithms for frequency analysis of acoustic signals which will produce results similar to cochlear frequency analysis and provide an alternative to traditional Fourier frequency analysis.